This application is based upon and claims benefit of priority of Japanese Patent Application No. Hei-11-262956 filed on Sep. 17, 1999, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a method of repairing a heat exchanger, such as a radiator for cooling an internal combustion engine, a condenser for an automobile airconditioner, or a heater core, and more particularly to a method of closing a hole in a damaged portion of an aluminum heat exchanger.
2. Description of Related Art
Aluminum heat exchangers are getting predominantly used in recent automobiles in place of copper heat exchangers. The copper heat exchangers can be repaired by soldering with a gas burner or the like, but the aluminum heat exchangers cannot be repaired by such a manner because the melting point of aluminum is low. Accordingly, a hole formed in a damaged aluminum heat exchanger core is usually repaired by closing the hole with an epoxy-resin-type adhesive material.
However, it takes a considerably long time to repair the damaged core with the epoxy-resin-type adhesive material because a long time, e.g., two or three hours, is required to cure the epoxy resin under the room temperature. The time required for curing the epoxy resin can be shortened if a high temperature oven is used. In this case, however, it is necessary to provide a costly high temperature oven for the repairing purpose.
Further, the conventional repair work has not been sufficiently complete because the aluminum heat exchanger is repaired under a method as shown in FIGS. 4A and 4B. That is, the epoxy-resin-type adhesive material 101 is directly coated on a damaged aluminum tube 102 to close a hole 103 formed therein, and then the adhesive material is cured. Therefore, the adhesive material flows over the vicinity of the hole 103, thereby making the coated layer thin. The hole 103 is not completely closed, or the once coated adhesive material tends to be peeled off in a short time.
The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an improved method of repairing the aluminum heat exchanger, and more particularly to provide such a method under which a quality repair work is performed in a short time without using a costly high temperature oven.
When an aluminum heat exchanger such as an aluminum radiator is damaged for some reason and liquid coolant contained therein leaks out from a damaged portion, the damaged portion is repaired under the method according to the present invention. The radiator is composed of upper and lower tanks, plural tubes connecting both tanks and corrugated fins disposed between neighboring tubes. All of those components are made of an aluminum alloy and brazed in a furnace to connect all the components into a single unit. When such a radiator is damaged, a hole is formed through a wall of the tube, and the coolant leaks out form the hole.
A certain area around the damaged portion including the hole is pressed down to form a cup-shaped depressed portion. The size of the depressed portion is made sufficiently large, preferably with the diameter of 2-20 times the size of the hole and with the depth of 1-8 mm. The depressed portion is degreased, washed and dried, and then an adhesive material composed of acrylic resin and a hardener is supplied to the depressed portion. The adhesive material retained in the depressed portion is cured for about 20 minutes under the room temperature. Thus, the hole in the damage portion is closed with the hardened adhesive material.
Since the adhesive material is retained in the depressed portion while it is being cured and is partly impregnated into the corrugated fins, the adhesive material having a sufficient thickness firmly sticks to the damaged portion without being peeled off afterwards. Since the acrylic resin is used as the adhesive material, it is quickly cured under the room temperature without using a high temperature oven.
The repairing method according to the present invention is applicable not only to the aluminum radiators but to other aluminum heat exchangers such as condensers or heater cores used in automotive air-conditioners.